It is already known to use winches for manually or automatically opening any type of shutters placed on roofs or on facades of buildings for the evacuation of smoke or for ventilation purposes, these shutters being particularly provided at the top of staircases, elevator wells and ducts of any sort which are found in domestic, commercial or industrial buildings. The shutters permit, when closed, to protect the staircases and other ducts against bad weather, and, when open, to ventilate the premises, especially when the weather is hot.
Moreover, these shutters or smoke outlets should open instantaneously in case of a discharge of smoke or noxious gases in order to avoid their spreading throughout the building.
The smoke outlets are provided with spring devices tending to open them, and they are kept closed by means of a releasable locking mechanism, such as a mechanical or electromagnetic lock, a thermal fuse or the winch operating the smoke outlets for ventilation purposes.
But all such mechanisms do not accomplish all the functions required by the new safety regulations.
The present invention remedies this disadvantage by providing a winch which can be operated manually or with the aid of a small motor, the winch having a drum on which is wound the control cable of the smoke outlet, and which is subjected to the control of radial electromagnetic release means having multiple blocking positions providing an immediate response for an instantaneous automatic opening of the smoke exhaust outlets or vents.